Landing gear for aircraft



Aug- 22, 1944 s. M. PARKER 2,356,468.

LANDING GEAR FOR AIRCRAFT Filed Aug. 1l, 1942 If/viA/rak .S'.M.PARKER Patented Aug, 22, 1944v 2,356,468 f LANDING GEAR Fon AIRCRAFT Sydney MacDonald Parker, Leamington Spa,

England, assignor to Company Limited, Lea

Automotive Products mington Spa, England Application August 11, 1942, Serial No. 454,419.l I

In Great Britain February 25, 1 942 s ciaims. (ci. 244-104) 'I'his invention relates to landing gear for-aircraft, and more particularly to mountings for landing wheels or equivalent landing members (such as endless tracks) which are capable of angular movementabout a substantially vertical axis to permit the aircraft to travel readily in a curved path when supported by its landing gear on the ground. Such landing members are the tailwheel of an aircraft having the well-known form of landing gear comprising two or more transversely spaced main wheels forward of the centre of gravity, and a single wheel near the tail of the aircraft, and the nose wheel of the more recent form of landing gear commonly referred to as the ricycle undercarriage,

'Ihese Ilanding members, -when deflected from their true fore-and-aft position by striking an obstruction or by any other cause, may tend to oscillate about their normal positions for a considerable period, throwing great strain-on the aircraft structure and rendering control difficult, and various measures have `been proposed to damp out such oscillations, such as friction'bands and other friction means, and hydraulic damping.

One known. kind of mounting for a. landing wheel or equivalent comprises a shockv absorber strut consisting of a cylinder and a plunger reciprocable therein, the cylinder of the strut being e aircraft framework and forming the sole connection between the wheel orequivalent and the aircraft, and my co-pending application Serial No. 424,974, filed December 30, 1941, describes a mounting of this kind. The primary object of the present invention is to provide improvements or modifications in the form of device described in the co-pending application above referred to.

It is an object of the present invention to provide a mounting for a landing wheel or equivalent landing member in which the frictionalU damping of the rotational movement of the plungll the cylinder Ill of,

secured to its lower end a sleeve ll forming an er is limited'to a predeterminedmaximum regardless of the load acting on the strut. o According tothe present invention, in amounting for a landing wheel or equivalent landing member a damping device acting'onftlfiepylinder member of thestrut isv arranged between the Saidv cylinder member and'fan intermediate mem,-

ber rotatable about-,the axis offthe cylinder with respect to bothfthe cylindermembe'rand the aircraft framework, the'rotary movement ofi'gthe intermediate .member being -ccmtrolled' by a' seciond: y'frietiona'lf"damping device exerting "a 'con'- stent resistance to rotary movement of said intermediate member.

The second frictional damping device is'pref erably manually adjustable to vary the resistance to rotary movement of the intermediate member. A

The intermediate member may comprise a sleeve surrounding the cylinder member, and itself surrounded by an outer sleeve supported in the aircraft framework, and the intermediate sleeve may be flanged at its lower end, a ring of friction material, being provided between the flange and an abutment surface on the cylinder member, the load on the strut being transmitted to the sleeve through the said abutment and flange.

The intermediate sleeve may be mounted in the outer sleeve on a thrust bearing. y

The rotation of the intermediate sleeve in the outer sleeve may be restrained by a friction band engaging one of the said sleeves and held against rotation with respect to the other sleeve, the friction band being for example in frictional engagement with the intermediate sleeve and housed in an annular recess in the outer sleeve, lugs on the ends of the friction band projecting through an aperture in the outer sleeve to prevent rotation of theband. tion band may-be urged towards each other by resilient means, the loading of which may be adjustable.

The invention is hereinafter described with reference to the accompanying drawing, in which:

Figure 1 is an elevation, partly in section, of one form of mounting according to the inver tion; and

Figure 2 is a-section` on ure 1.

In the form of the line 2 2 of Figmounting shownin Figure 1, a resilient telescopic strut has integral part of the cylinder` assembly. From thesleeve Il projects abracket- I2 tov which, at a point `I3 offset I4 inlvvhiclr` the forked'arm'V Wheel 5 is mounted, the arm I 4 being so.' arranged that Vthe wheel axis is onthe'opposite side Vof' theA cylinder axis Y tothe p ivotof the arm.` 4Atubular plunger y'lli pivotally secured to the .arm I4 yat, I 1: near its y pivoted end extends into lthecylinder` |,0, and. -is

formed'atitsfupper. end ywith an enlarged head I8 fitting closely within lthe cylinder,v `the head yhaving its peripheralsurface 2| which engages the wall of the cylinder of substantially part# spherical form, so that it may rock slightly dur ing the movements of the arm 'I4 about its pivot.

The ends of the fricsomewhat from the axis of the cylinder I0, ispiv'otally secured one ,end of a application Serial No. 424,974, but .is not described l herein as it forms no part of the present invention. The plunger tube I6 itself is closed at its lower e'nd and, with the lower part 23 ofthe cylinder I0, constitutes'an oleo-pneumatic. shock absorber, the air chamber of which is the plunger tube, whilst the damping is controlled by orifices (not shown) in the plunger head I8. The air is confined in the plunger tube by a oating piston (not shown) mounted therein. The plunger head I6 is provided with suitable packing means 25 to prevent the escape of the shock absorber liquid into the part of the cylinder below it.

It will be readily understood that as the thrust transmitted between the strut and the aircraft is transmitted through the ring 34 of friction material the load on the latter, and therefore the friction damping between the cylinder I0 and thegsleeve 26, is proportional to the load on the strut at any instant.` When the aircraft is airborne the friction material is unloaded and the strut is free to turn under the influence of the self-centering mechanism.

So long as the load on the strut is small enough for the turning force exerted on the sleeve 26 by the frictional drag ofthe ring 34 to be less than the resistance to turning of the sleeve 26 created by the friction band 4|, the degree of damping rises and falls 'with the load.

The cylinder I0 is rotatably mounted ina bearing sleeve 26 which surrounds its lower. end and is itself rotatable ln an outer sleeve 21 from which projects a lug 28 in which is provided a hole 29to receive a mounting spindle about which the mounting can swing for retraction. A sec .ond bearing for the cylinder is provided at 3| on` the stemV supporting the self-centering mechamsm.

The sleeve 26 surrounding the lower end of the cylinder is anged at its lower end, the flange 32 having a flat annular lower face lying If, however, the load on the friction ring 34 rises suiciently to turnthe sleeve 26 against the resistance of the band4l, the sleeve 26 turns relatively to the sleeve 21, and .the degree fof friction .damping is, therefore, limited by the setting of the band 4|.

A plurality of discs of friction material alternating with metal discs may be employed between the enlargement 43 on the sleeve and the bearing sleeve, the friction discs being rotationally. coupled to one member and the metal i discs to the other, thus increasing the frctional opposite to the flat upper surface of an env largement 33 at the lower end of the sleeve Between the enlargement 33 and the flange 32 on the bearing sleeve, is mounted a ring 34l of friction material either loose or securedto one or other of the surfaces, the combination forming in effect a friction clutch. The cylinder has a smalldegree of longitudinal play in the bearing sleeve 26, being retained therein by a collar 35 secured to the cylinder above the sleeve, and the load on the strut is taken solely through the friction material 34, with the result that the pressure thereon varies with the load on the strut and becomes zero when the aircraft is airborne. The resistance to turning of the cylinder inthe sleeve 26 is clearly dependent on the pressure applied to the clutch and therefore is Y mounted a friction damping ban' 4| located against rotational movement with respect to the sleeve 21 and engaging the outer surface of the sleeve 26. The friction band 4| comprises a plurality of segments 42 of friction material secured to a channel-shaped split carrier ring 43, the two ends of the ring being provided with lugs 44 which project through an aperture 45 in the sleeve 21, and are drawn towards each other to cause the band 4| to grip the sleeve 26 by a spring 46 mounted on a bolt 41 passing through the two lugs 44`, the loading of the spring being varied by adjustingra nut;y 48 on the bolt 41. The band 4| is prevented from turning in the sleeve 21 by the engagement of the lugs 44 with the sides of the aperture 45 .and it, therefore,

serves to resist the rotational movement of the sleeve 26.

resistance to rotation.

What I claim is: l. In aircraft landing gear including a landing element, a telescoping piston and cylinder shock absorber supporting said landing element from the aircraft body, and means mounting said shock absorber for rotary motion aboutits long axis; means rotatable about said cylinder, stationary adjustable braking means acting with uniform braking effect on the means rotatable 'about said cylinder and friction means interposed intermediate said cylinder and the means rotatable thereabout for retarding relative rotary motion of the two to an extent increasing as a function of the load on the shock absorber.

2. In aircraft landing gear including a landing element, a telescopi'ng piston and cylinder shock absorber supporting said landing element from the aircraft body, and means mounting said shock absorber for rotary motion about its long axis; a flanged sleeve surrounding the cylinder of the shock absorber, said cylinder having thereon a coacting flange, an annulus of frictional material disposed intermediate said flanges whereby rotation of the cylinder relative to the sleeve will be retarded to an extent depending upon the pressure between the t'wo flanges, and stationary braking means for frictionally retarding rotation of said sleeve. L

3. In aircraft landing gear including a land- .ing element, a telescoping piston and cylinder shock absorber .supporting said landing element from the aircraft body,l and means mounting said shock absorber for rotary motion about its long'axis; -a flanged sleeve surrounding the cylinder of the shock absorber, said cylinder having thereon a coacting flange, an annulus of frictional material disposedV intermediatesaid flanges whereby rotation of the cylinder relative to the sleeve'will be retarded to an extent de pending upon the pressure between the two flanges, stationary braking means for frictionally retardingrotation of said sleeve, and means for adjusting the pressure of said braking means to adiustably predetermine Y the braking effect 4. Anali-'craft landing gear including a landing element, a telescoping-piston and cylinder shock absorber supporting said landing element `from the aircraft body, and means mounting said shock absorber for rotary motion about its long axis; a angedsleeve surrounding the cylinder of the shock absorber, said cylinder having thereon a coacting ange, an annulus of frictional material disposed intermediate said flanges whereby rotation of the cylinder relative to the sleeve will be retarded to an extent depending upon the pressure between the two flanges, a second sleeve surrounding the first mentioned sleeve, means anchoring said second sleeve against rotation, and braking means mounted in said second sleeve in a position to act on the rst whereby the rotative force applied tothe rst sleeve will vary with the shock absorber load while the resistance of the braking means thereon will remain constant. 5. An aircraft landing gear including a landing element, a telescoping piston and cylinder shock 'absorber supporting said landing element from the` aircraft body, and means mounting said shock absorber for rotary motion about its', long axis; a flanged sleeve surrounding the cylinder of the shock absorber, said cylinder having thereon a coacting ilange, an annulus of frictional material disposedintermediate said flanges whereby rotation of the cylinder relative to the sleeve will be retarded to an extent depending upon the pressure `between the two llanges, a second sleeve surrounding the first mentioned sleeve, means anchoring said second sleeve against rotation, and a second annulus of frictional material disposed in said second sleeve, a band surrounding said second annulus of frictional material, said band being xed against rotation with respect to said second sleeve, and means for adjusting the circumferential dimension of said band tol vary the compression exerted by the second annulus of frictional material.

6. In aircraft landing gear' including a landing element, a telescoping piston and cylinder shock absorber supporting the element from the aircraft, means mounting said shock absorber for rotary motion about its long axis, and means biasing the same to one angular positionin which the landing'element is aligned; means rotatable `about fsaid cylinder, vstationary adjustable braktent increasing as a ing means. acting with uniform braking effect on the means rotatable about said cylinder and friction means interposed intermediate said cylinder and the means rotatable thereabout for retarding relative rotary motion of the two to an exfunction of the load on the shock absorber.

'7. In aircraft landing gear including a landing e1ement, a telescoping piston and cylinder shock absorber supporting the element from the aircraft, means mounting said shock absorber for rotary motion about its long axis, and means biasing. the same to one angular position in which the landing element is aligned; a iianged sleeve surrounding the cylinder of the shock absorber, said cylinder` having thereon a coacting ilange, an annulus of frictional material disposed intermediate said ilanges whereby rotation of the cylinder relative'to the sleeve will be retarded to`an extent depending upon the pressure between the two flanges, and braking means for frictionally retarding rotation of said sleeve.

8. In aircraft landing gear including a landing element, a telescoping piston and cylindershock absorber supporting the element from the aircraftmeans mounting said shock absorber for rotary motion about its long axis, and means biasing the same to one angular position in which the landing element is aligned; a flanged sleeve surrounding the cylinder of the shock absorber, said cylinder having thereon a coacting flange, an annulus of frictional material disposed intermediate said anges whereby rotation of the cylinder relative to the sleeve Will be retardedto an extent depending upon'the pressure between the two flanges, a second sleeve surrounding the rst mentioned sleeve, means anchoring said second sleeve against rotation, and asecond annulus of frictional material disposed in said second sleeve, a band surrounding said second annulus of frictional material, said band being I fixed againstrotation with respect to said second sleeve, and means -for adjusting the circumferential dimension of said band to vary the compression exerted by the second annulus of 4frictional material.

SYDNEY MACDONALD 

